Israeli security officials said that the two suspects, ages 17 and 18, had confessed and carried out a reconstruction of the attack.

The announcement was greeted with disbelief in Awarta, where many of the residents, including relatives of the suspects, have condemned the brutal killing of Ehud Fogel, who was known as Udi; his wife, Ruth; and three of their children, Yoav, 11, Elad, 4, and Hadas, a baby girl of 3 months.

Two other young children who were sleeping in the house were unharmed. An older sister, Tamar, 12, had been out at a youth activity at the time of the killings and returned to discover the bodies.

The prime minister of Israel, Benjamin Netanyahu, commended the security forces on their effort. “For the family, this is not a complete answer, but without it they could not be given even a partial answer,” he said.

Israeli security forces had been combing the village of Awarta for weeks after the March 11 attack. The attack shocked Israelis across the political spectrum and was denounced by leaders of the Palestinian Authority, including President Mahmoud Abbas.

The younger of the two suspects, Hakim Awad, was arrested on April 5. That led to the arrest of the second suspect, Amjad Awad, a distant cousin, five days later, according to Israeli officials.

The investigation was carried out jointly by the Israeli military, the Shin Bet internal security agency and the police. But there were variations in some of the details of the investigation from the different bodies.

The Shin Bet said in a statement that the two suspects, a high school pupil and a first-year student at The Open University, were identified with a Palestinian leftist militant group, the Popular Front for the Liberation of Palestine, although it was not clear whether the organization had any role in the attack.

The Shin Bet emphasized that the attack had been planned and that days before the suspects had tried to obtain a gun through a Popular Front member in Awarta who refused to help.

But Col. Nimrod Aloni, the Israeli Army’s regional commander of the northern West Bank who led the investigation on behalf of the military, said in a conference call with reporters that the killings did not seem planned and that the suspects were not connected to any organization. He said that he believed they had wanted to enter a settlement as a test of courage and to steal weapons.

What actually happened that night in Itamar is not in dispute. Officials said that the two suspects walked the mile or so from Awarta to the perimeter fence that surrounds Itamar armed with knives, a wire cutter and some kind of hoods or ski masks.

After crossing the fence, they entered the house next door to the Fogels. It belonged to the Hai family and was empty. There they stole an M-16 assault rifle, clips and a protective vest, officials said.

Photo

Israeli forces combed Awarta after the attack in Itamar.Credit
The New York Times

They proceeded to the Fogel house, where they immediately killed the two young boys, according to the Shin Bet, before entering the parents’ bedroom. The parents struggled with the intruders and were killed, shot with the weapon stolen from their neighbors’ house and stabbed with knives.

The killers left the house but returned again for another gun, which they stole. At that point, according to both the Shin Bet and the military, the baby girl woke up and cried, so they stabbed her to death as well.

The extended Awad clan makes up about half of Awarta, which has a population of around 7,000.

The mayor of Awarta, Qais Awad, a distant relative of the suspects, said on Sunday that he had “many doubts about this Israeli story” and demanded an independent international investigation. “From the first moment,” he said, “we condemned the killing of children.”

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About 35 residents of Awarta remain in Israeli detention, and six relatives of the main suspects are under arrest, suspected of aiding the killers after the fact, according to the Shin Bet.

One of the six is Hassan Awad, the deputy mayor of Awarta and an uncle of Hakim, the younger suspect.

In late March, before his arrest, the deputy mayor met with reporters in Awarta and denounced the Itamar killings, saying that the murder of children went against Arab and Muslim tradition.

Nouf Salim Awad, 37, the mother of Hakim, said that her son was in his bedroom on the Friday night of the killings. The next morning, she said, Hakim, one of seven children, got dressed and went out to school but returned home, saying that the village was under an army curfew.

“If I knew that my son was behind this, I would have taken him myself and handed him over to the Palestinian Authority,” she said, adding that she did not believe he could have been involved.

“There are only two possibilities,” she said. “Either he became crazy, or he was forced to confess.”

In Itamar, the arrests brought little comfort. Haya Hai, 30, the neighbor whose house the suspects entered first, said, “We hope they will receive the same justice as the Fogel family. They should be given the death penalty.”

That is unlikely, since the death penalty has never been used in Israel against those carrying out terrorist attacks.

Ms. Hai, a mother of four, said that Sunday’s news only added to her “bad feeling,” noting, “I heard that the killers used our weapon to kill them.”

The attack on the bus set off days of cross-border fighting between Israel and Gaza during which 19 Palestinians were killed, several of them civilians.

A version of this article appears in print on April 18, 2011, on Page A8 of the New York edition with the headline: 2 Palestinian Teens Held In Killing of Israeli Family. Order Reprints|Today's Paper|Subscribe